The present invention relates to a device for preventing a flexible line more particularly, a flexible pipe, from twisting.
The present invention is especially applicable to the offshore production of oil products.
The bottom/surface connections of floating production systems use flexible pipes which are disposed in the form of a catenary, this configuration accommodating the horizontal and vertical movements of the floating support. When this support is an oil ship or semisubmersible platform, a swivel or revolving joint allows to rotate about the head of the flexible pipe.
If the revolving joint is perfect (without friction) and if the oil ship remains in the vertical plane of the flexible pipe, no twisting is induced in the flexible pipe.
On the other hand, if the revolving joint is not perfect, which is practically always the case (in particular in the case of high pressure revolving joints and in the case of movements outside the above mentioned plane), a twist appears in the flexible pipe even if the oil ship keeps a constant heading.
Such twists are prejudicial to the longevity of the line, particularly because of the wear which they generate by friction of the sheathing layers on each other. In addition, these twists cause reactions which may be harmful for the fixing points at the ends of the flexible line and more generally for the supports of these fixing points.
The device of the present invention avoids the twisting of the flexible pipe, which reduces the stresses in the sheathing layers generally forming the flexible pipes and reduces warping of the flexible pipe and consequently the flexions.